In an open flask, 10 mL of 1.5 M NaBr in pH 6.2 phosphate buffer (0.23 M in PO4) or pH 4.2 phosphate buffer (5% NaH2PO4) was added to a solution of 1 mmol of substrate dissolved in 9.75 mL of distilled 1,4- dioxane. To this mixture was added a freshly made solution of diphenyl ditelluride (1e, 0.25 mL of a 10 mM stock in 1,4-dioxane, 2.5 μmol, 0.25 mol % relative to substrate) followed by the addition of 8.8 M H2O2 according to Table 3. The reaction mixture was stirred at room temperature for the appropriate amount of time and was then diluted with 10 mL of water. The resulting solution was extracted with EtOAc (3 × 10 mL), and the combined organic extracts were washed with 0.5 M NaHSO3 (5 mL) and brine (10 mL), dried over MgSO4, and concentrated. Yields reported below are the mean of duplicate runs. N-(4-Bromophenyl)morpholine (21):28 product isolated as a tan solid (224 ± 1 mg, 93% yield). Mp 111-113 °C (lit.28 mp 111-112 °C).
